1. Field of the Invention
This invention relates generally to low dielectric constant materials, and more particularly to chemical vapor deposition (CVD) processes for making these materials, and the use of these materials as dielectric layers in microelectronic devices.
2. Description of the Related Art
As the dimensions of microelectronic devices become smaller, the importance of the physical properties of the materials used in their manufacture becomes more important. This is particularly true of the dielectric materials that are used to insulate metal lines and vias from one another because of the contributions to capacitance that these materials make. Silicon dioxide has been employed within the industry as a dielectric material for the manufacture of devices for nearly three decades, but may become less suitable in the future because of its relatively high dielectric constant (k˜4.1).
A number of fluorinated materials have been studied as possible replacements for silicon dioxide. U.S. Pat. No. 5,563,105 discloses a chemical vapor deposition (CVD) process employing SiF4 and tetraethoxysilane (TEOS) to form a fluorosilicate glass, which is stated to have lower water absorption than a sample formed from C2F6. U.S. Pat. No. 5,703,404 discloses silicon oxide films containing Si-F bonds through the use of fluorosilanes. U.S. Pat. No. 5,876,798 discloses the use of fluorotriethoxysilane (FTES). The use of fluorinated compounds containing carbon-carbon double bonds is disclosed in U.S. Pat. Nos. 5,989,998. 6,051,321 discloses the use of fluorinated aromatic compounds. U.S. Pat. No. 5,900,290 discloses the use of octafluorocyclobutane, as does T. Shirafuji et al., “PE-CVD of Fluorocarbon/SiO Composite Thin Films Using C4F8 and HMDSO,” Plasmas and Polymers, Vol. 4, No. 1, p. 57, 1999. Other references in this regard are Indrajit Baneree, et al., “Characterization of Chemical Vapor Deposited Amorphous Fluorocarbons for Low Dielectric Constant Interlayer Dielectrics.” J. Electrochem. Soc., Vol. 146(6), p. 2219, 1999; C. B. Labelle, et al., DUMIC, pg. 1998, 1997; and Sang-Soo Han, et. al., “Deposition of Fluorinated Amorphous Carbon Thin Films as a Low-Dielectric Constant Material.” J. Electrochem. Soc., Vol. 146(9), p. 3383, 1999.
Amorphous fluorinated carbon (a-C:F) materials are a promising class of fluorinated materials. However, the known materials have been shown to be severely lacking in one or more aspects for use in microelectronics manufacturing. Some of the known issues with currently known a-C:F materials include: low thermal stability (e.g., less than 300° C. at k˜2.2 or below), anisotropic dielectric constant (in-plane vs. out-of-plane), low mechanical stability, low modulus and glass transition temperature, low adhesion strength, particularly at elevated processing temperatures, fluorine out-diffusion during subsequent thermal treatments, and fluorine etching of existing structures during processing.
Therefore, there remains a need for fluorinated carbon films having better properties more suitable for use in microelectronics manufacturing, and for processes for producing such films that can be readily integrated into fabrication process flows.